The term "polyphenylene ether resins" is well known as defining a class of thermoplastic materials which possess outstanding physical properties, including hydrolytic stability, dimensional stability and excellent dielectric characteristics. Methods of preparation are known in the art and described in the patent literature, e.g., Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875 and Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358, incorporated herein by reference to save unnecessary detail. Other patents which show the preparation of polyphenylene ether resins include Bennett and Cooper, U.S. Pat. Nos. 3,639,656 and 3,838,102, as well as Cooper and Bennett, U.S. Pat. Nos. 3,642,699, 3,661,849 and 3,733,299, also incorporated herein by reference.
It is known that when the polyphenylene ether resins are combined with styrene resins, the resulting compositions possess properties which are improved over the corresponding properties of either resin alone. See Cizek, U.S. Pat. No. 3,383,435, the disclosure of which is incorporated herein by reference.
A shortcoming of some thermoplastic materials is the tendency to accumulate surface electrostatic charges. Thermoplastic materials having characteristic resistivities in the range of from about 10.sup.10 to 10.sup.12 ohms normally do not hold static charges. On the other hand, thermoplastic materials characterized by resistivities in the range of from about 10.sup.16 to 10.sup.18 ohms often develop high static voltages, and polyphenylene ether resins and composites of polyphenylene ether resins with styrene resins fall into this latter group.
Such static charges develop during processing and/or during normal use after molding. They are undesirable for a number of reasons: surface static charges readily attract dust and other contaminants which are unsightly and difficult to clean; often the contaminants or static charges themselves cause processing problems; the charges may accumulate to a level where an unpleasant electrical shock is imparted upon touching; in addition, a high level of static charges in a molded part covering sensitive electronic equipment may be undesirable.
Previous attempts to produce essentially static-free polyphenylene ether compositions have not been entirely satisfactory. The present invention is based on the discovery that triethanolamine, toluene sulfonic acid and sodium lauryl sulfate, when used in combination in a polyphenylene ether composition, readily dissipate static charges and results in compositions which are essentially free from the aforementioned shortcomings of prior art compositions.